The present invention relates to a device for counting the turns unwinding from weft feeders of weaving looms, allowing an automatic adjustment of the speed of said feeders.
Typically weft feeders are devices provided with a fixed drum on which a rotating arm, moved by an asynchronous motor, winds a plurality of thread turns which are progressively unwound by the loom or by another textile machine; the tension of the thread at the output of the feeder is controlled by a braking means which can be constituted by a ring of bristles or by a set of metallic laminae.
The reserve of turns wound on the fixed drum varies between a maximum and a minimum value indicated by corresponding mechanical and/or optical feelers.
In order to avoid disadvantages deriving from continuous stops and starts of the motor, which can produce tangling and/or undesirable variations in the tension of the thread, it is important that the reserve of turns be always comprised between said maximum and minimum values, and this implies that the feed speed of the turns of the reserve must coincide, or substantially coincide, with the removal rate. The latter, however, is generally unknown and in any case is significantly variable during the operation of the textile machine, especially in the case of shuttle-less looms, such as jet looms and the like.